Studies of Zeolite Acidity

本项目包括一系列研究，解决沸石和相关材料的酸度问题。对H-ZSM-5中的中间体进行了光谱研究——核磁共振是主要工具——以表征化学计量学和反应性已分别建立的物质；目的是确定中间体的结构，它们与沸石晶格相互作用的性质，以及它们进行进一步转化的势垒高度。通过一系列表征良好的H-Y分子筛的制备和酸度研究，考察了各种脱铝工艺的影响以及框架铝和非框架铝浓度的作用；酸度替代品的使用包括温度程序解吸和热重分析胺，烷烃裂化，和碱金属中毒。制备并检测了一系列金属取代的ZSM-5和ALPO-5分子系列，以确定这些材料的相对酸强度，并确定维持框架中金属离子的必要条件。沸石作为催化剂和分离介质已广泛应用于石油和化工行业。尽管如此，影响他们表现的因素却知之甚少。这项工作有望为沸石和相关框架材料的应用提供更合理的设计方法，更好地控制合成沸石的质量，以及已知或新的框架材料在化学加工，环境控制和其他领域的新应用。

This project consists of a set of studies addressing the issue of acidity in zeolites and related materials. Intermediates in H-ZSM-5 are studied spectroscopically - nuclear magnetic resonance being the prime tool - to characterize species whose stoichiometry and reactivity have been established separately; the objectives are the determination of the structure of the intermediates, the nature of their interactions with the zeolite lattice, and the barrier heights for them to undergo further transformations. The effect of various dealumination procedures and the roles of framework and nonframework aluminum concentrations are examined by preparation of and investigation of the acidity of a series of well-characterized H-Y zeolites; acidity surrogates used include temperature- programmed desorption and thermal gravimetric analysis of amines, alkane cracking, and alkali-metal poisoning. A series of metal-substituted ZSM-5 and ALPO-5 molecular series are prepared and examined to determine the relative acid strengths of these materials and to determine the necessary conditions for maintaining the metal ions in the framework. Zeolites are already widely used in the petroleum and chemicals industries both as catalysts and separations media. Despite this, factors influencing their performance are poorly understood. This work promises an approach to more rational design for applications of zeolites and related framework materials, better quality control over synthetic zeolites, and possible new applications of known or new framework materials in chemical processing, environmental control, and other areas.